In this work is demonstrated that the Surface Resistance (SR) technique can be applied to study the different interactions of anions, such as, perchlorate, sulphate and benzenesulphonate and also a cation as Cu(II), with a gold film surface, even when the metal film surface is partially blocked with an electroactive polymer film. The electroactive polymer poly(o-aminophenol) (POAP) was employed to cover the surface of the gold film electrode. Resistometric changes were detected even after the metal surface was completely covered with the polymer. Dependence of the resistance change on the external electrolyte composition for polymer thicknesses lower than 0.25 mC cm-2 was attributed to a competition, at the gold film surface, between the redox process of the polymer and adsorption of different species in the electrolyte. This result points to a discontinuous character of the polymer for thicknesses lower than 0.25 mC cm-2 at the metal?polymer interface. For polymer thicknesses higher than 0.8 mC cm-2, the resistometric response becomes independent of both the external electrolyte composition and the polymer thickness. Thus, polymer thicknesses higher than 0.8 mC cm-2 seem to be compact enough at the metal/polymer interface to prevent the interaction of species in the supporting electrolyte with the gold film surface. However, the resistometric changes observed, were attributed to the redox conversion of the polymer. In this connection, the redox conversion of POAP from amine to imine groups leads to an increase of the gold film resistance. This increase was explained as a transition from specular to diffuse scattering of the conduction electrons of gold at the gold/POAP interface due to a less compact distribution of oxidised sites (imine) as compared with those of the reduced centers (amine).